I have Lenovo 300 N100 laptop, suddenly its screen goes dark after boot. At starting when i press Fn+F7 the LCD light comes for few seconds and then vanishes, now the duration of the light is even less than a second. I have checked by connecting other monitor and it works properly. On consulting on internet help I come to know that the backlight mayb not working, and now I couldnt able to get any assistance for replacing the backlight. So I need the procedure to replace the backlight CCLF of my laptop thank you

The backlights in your monitor are part of the display panel itself and cannot be changed..
You may need to replace the entire display panel.
However, start by having the inverter which runs the display panel backlighting checked as the fault may lay in it rather then in the panel itself.
Now, you must be VERY careful when handling this inverter as it is more then capable of giving you a nasty electric shock.
To be safe, have the panel and the inverter checked by a professional.
NEVER handle an inverter that is connected to a supply rail..
The inverter is usually located inside the monitor housing of the laptop and care must be taken to open up the housing. Most housings are held together with formed plastic clips and you simply prise the fascia off the front very carefully. DO NOT apply any pressure to the display panel during this.
If the inverter is not in the monitor housing, then it will be under the keyboard and in this case, I would advise you take the laptop to a professional as replacing the wrong screw into the wrong hole can cause serious damage to the mainboard and destroy the laptop.